Book spine



FIG. 1 is a perspective view of a book spine showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a front elevational view thereof; and

FIG. 5 is a side elevational view thereof.

The broken line showing of the binder in FIG. 1 is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a book spine, as shown and described. 